The long-term goal of this proposal is to elucidate the neural substrate underlying audio-vocal integration in mammals. Echolocating bats are ideal for studying audio-vocal integration because they continually modify the parameters of their vocalizations based upon characteristics of the returning echo. In the horseshoe bat, the midbrain paralemniscal tegmentum (PL) is believed to be centrally involved in the coordination of auditory input with vocalization. Afferent projections from several places along the main auditory pathways converge within the PL, and PL efferents are known to influence vocalization. The PL is composed of at least five subpopulations distinguishable by their response properties and cytoarchitecture, and each is potentially involved in the modulation of different motor patterns. The goal of this proposal is to identify the pharmacological nature of the afferent and efferent projection patterns of each PL subdivision, and the contributions of each region to audio-motor integration. Specifically, biotin-conjugated Ibotenic acid (NMDA agonist) and muscimol (GABA agonist) will be injected into each subdivision while monitoring vocalizations in the awake and behaving animal. Spontaneously vocalizing bats will be presented with artificial echoes, and the parameters of succeeding vocalizations will be analyzed. Afterwards, the brain will be examined histologically. The contributions of each PL subdivision to audio-vocal integration will be assessed, along with pharmacology, a specific mapping of injection sites, cytoarchitectures, and projection patterns. Ultimately this work should lead to improved speech therapies for hearing impaired humans.